In many work environments, particularly in factories, warehouses and the like, very large spaces are provided which must be lit by large overhead lighting systems. In such spaces, particularly in factories or foundries, there is substantial airborne dirt and dust which will rise to the ceilings of the building and accumulate on the overhead light fixtures. This necessitates periodic cleaning of the fixtures, which is often difficult to do because they are mounted in very high ceilings so that access to them is difficult.
In addition, because large overhead industrial light fixtures create a large amount of heat there must be a means to remove the heat from the fixture so that it does not damage the thermally vulnerable electrical components in the ballast. For this reason most industrial fixtures use open reflectors which allow circulating air to keep all components cool. The open reflector arrangement itself serves to draw dirt and dust particles towards the light fixture and increases the possibility of dust and dirt accumulating on the light fixture.
In some industrial light fixtures, the reflector is sealed with the intent of excluding dust and dirt from the interior of the fixture. Normally a lens is provided over the bottom of the reflector. This arrangement may keep the interior of the lens clean but there is no mechanism for keeping the exterior of the lens clean.
In some sealed units a ring is provided around the exterior of the lens to provide a barrier to circulating dust and dirt. This works to reduce the amount of airborne dust and dirt circulating near the lens but does not provide a mechanism for insuring that this dust and dirt falls away from the lens without contacting it.
It is an object of the present invention to provide a light fixture which will resist the accumulation of dirt and dust on the exterior of the lens thereof.
Another object of the present invention is to provide a high intensity light fixture which will resist the accumulation of dirt and dust on its light diffusing lens.
Yet another object of the present invention is to provide a light fixture of the character described which is relatively inexpensive to manufacture and simple to assemble.
A further object of the present invention is to provide a light fixture of the character described which is relatively simple to disassemble for cleaning when necessary.
In accordance with an aspect of the present invention, an electrical light fixture is provided which includes a lamp head having an open end that defines a peripheral edge. A light bulb, such as a high intensity discharge bulb, is mounted within the housing for distributing light through the open end thereof. A reflector is mounted in the housing for reflecting light produced by the bulb through the open end of the housing. The reflector has a generally elliptical shape in cross section and is positioned relative to the bulb to focus light from the bulb at a predetermined focal point. This produces a high intensity light as well as substantial heat in the area of that focal point.
A transparent lens is mounted on the housing adjacent the peripheral edge thereof and means are provided for creating a dust seal between the lens and the housing to prevent dust from entering into the housing and accumulating on the reflector or the light bulb. An extension ring is removably mounted on the open end of the lamp housing, with the ring extending away from the housing and the lens therein. This defines an airspace adjacent the lens and within the ring. A layer of warm air heated by the bulb will thus form and it is trapped within the ring due to convection. This warm air layer forms a barrier to dust particles approaching the light fixture and will cause dust particles to fall away from the lens due to gravity. Thus, accumulation of dust on the lens is reduced.